In a technical field related with a work machine such as an excavator, as disclosed in Patent Literature 1, there is known a work machine that controls a working implement so that a blade tip of a bucket moves along a target excavating topography (a design surface) indicating a target shape of an excavation target.
In the specification, a control for causing the blade tip of the bucket of the working implement to move along the target excavating topography will be referred to as a leveling assist control. In the leveling assist control, a target blade tip speed of the bucket is determined from a distance between the target excavating topography and the current blade tip position of the bucket, and the determined target blade tip speed is added to the blade tip speed counteracting the blade tip speed of the bucket in response to at least one of the arm operation amount and the bucket operation amount by the operator. Then, a target boom speed is calculated from the added value. Further, the target boom speed is corrected (compensated by integration) by using a correction amount obtained by the integration in time of the distance between the target excavating topography and the past blade tip position of the bucket, and the boom cylinder is controlled based on the target boom speed compensated by integration. In the leveling assist control using the compensation by integration, the boom cylinder is controlled so that the boom is raised when the blade tip of the bucket digs the target excavating topography.